1. Field of the Invention
The present invention relates to an apparatus for removing volatile material from solids. More particularly, the invention relates to an apparatus for removing hydrocarbons from earth, dirt, clay, drilling mud and the like. More particularly the invention relates to an apparatus including a heated rotary kiln having special sealing means for the shaft, solids removal apparatus and unique firing arrangement.
2. Related Information
Due to environmental concerns the removal of volatile material from solids has become an important process. The removal of hydrocarbons which have soaked into the ground over a period of time is now known as "remediation" and the number of recognized sites has grown astronomically. Former refinery and chemical manufacturing and storage facilities are prime candidates. Even the simple corner where a gasoline service station once stood is a candidate for "remediation". Other locations where remediation may be desirable or required are clothes cleaners, storage yards, junk yards, auto race tracks, auto repair shops and garbage dumps. Typically the soil is removed and taken to a remote location for storage until the volatile materials have dissipated into the atmosphere.
Another area in which volatile materials must be removed from solids is the reclamation of petroleum lubricated drilling fluids used in the exploration and production of petroleum oils. The drilling fluid, referred to as "mud", serves several purposes, the most important of which includes cooling and lubricating the bit and removing drilled solids, or cuttings, from the borehole. While it is essentially a water based, flowable composition, the drilling mud is frequently compounded with a lubricant material such as diesel, crude oil or other non-water petroleum based constituent to facilitate the mud's lubricating characteristics.
The mud is usually contained in a mud pit, which is connected by way of a mud line and mud pump to a hose and swivel used to inject the mud into the top of the drill pipe. The returning mud, combined with the cuttings, is captured in a mud return pipe and recirculated through the drill pipe.
When the concentration of the drill cuttings in the mud rises too high, recirculation of the mud becomes a problem. In order for the mud to perform its several functions, its viscosity, density and other properties must be maintained within acceptable limits. The drill cuttings adversely affect these properties thus reducing the carrying capacity of the mud and damaging the drilling equipment.
To allow for effective recirculation, the mud is usually separated from the cuttings prior to being recycled through the drill string. The cuttings are then disposed of as waste which presents a problem when the lubricating properties of the mud have been enhanced by the addition of hydrocarbons. Because of the hydrocarbons in the cuttings a hazardous waste problem is presented. Upon completion of the use of the mud in the well, the mud itself becomes waste which must be remediated for the same reasons. Historically, the contaminated cuttings and muds were diluted by mixing, and hauled to remote sites for disposal in landfills. This, however, also presents a problem in that the landfill then becomes a "hazardous" waste site leaving the dumper liable for environmental damages indefinitely.
Decontaminating the materials is more attractive. Treatment processes heretofore available to remove oil or other hydrocarbons from cuttings and mud include distillation, solvent washing, and mud burning. While these processes are effective to varying degrees at stripping the hydrocarbon contaminants from cuttings and mud particulates and rendering them environmentally clean, the processes remain problematic in that of disposal of the liquid or vapor from the disassociated contaminant.
There are several patents on rotary kilns specifically designed to remove volatile hydrocarbons from solid material such as soil. See for example U.S. Pat. Nos. 5,152,233; 5,199,354; 5,302,118, and 5,378,059. All of the rotary kilns are gas fired with the hot combustion gases being directed into the drum to heat the solids. When the solids have a substantial quantity of hydrocarbonaceous material an explosion hazard may be present. In addition, when the flame is applied directly to the contaminated materials, the solids are burned so that the contaminants are consumed and turned into smoke.
One feature of the present invention is to provide an apparatus to remove volatile contaminants from solids, such as cuttings removed from drilling mud, to render environmentally safe and disposable solids while recovering and recycling the disassociated hydrocarbons.
Another feature of the invention is that the volatile hydrocarbons are isolated from the fired heating elements to prevent an explosion hazard and the rotary kiln is sealed so as to prevent oxygen from reaching the heated volatile materials. Other features of the present invention include a kiln in which the solids are maintained in a particulate state and dust is controlled.